Wait for pre-checks the same way as we do with post-checks

[not-raspberry]

Running a service with execute and at least one check may fail if the previous service didn't terminate on time:

1. Process X₁ is ran with the executor.
2. SIGTERM is sent to the process X₁ but the service takes some time to tear down
3. Process X₂ is ran with the executor - pre-checks fail because they see the previous service.
4. X₁ terminates after some time but it's too late - X₂'s executor failed.

DRY polling - currently there is a simple wait_until implementation in test.wait and a polling loop inside the execute function. There will be another polling for the pre-checks so the rule of three has to be applied.